1. Field of the Invention
The present invention relates to a circuit of processing and providing electric power. More particularly, the present invention relates to a power circuit and a charge pumping circuit.
2. Description of Related Art
Conventional power circuits have a defect that when an output end has a load current, a voltage drop occurs, which is caused by an equivalent resistance of a switch in the power circuit when the load current passes through. Here, the output voltage is lower than an object voltage, and the differential value differs as different load currents and switch resistances.
Under the requirement for the application of voltage with high stability and high precision, a linear voltage regulator of low voltage drop is generally used at an output end of a power circuit so as to stabilize the output voltage. However, it is disadvantageous that the output capacitance of one linear voltage regulator is added. The capacitance usually occupies a larger area in an integrated circuit, and even an external device must be used, such that the cost is increased. In a multi-power system, the cost waste is more obvious.
FIGS. 1a and 1b show power circuits according to a conventional art. The power circuit in FIG. 1a performs a voltage transformation first, and then performs a voltage regulation. As shown in FIG. 1a, the power circuit 100a includes a power processing circuit 102a, a switch 104a, a first capacitor 106a, a linear voltage regulator 108a, and a second capacitor 116a. The power processing circuit 102a has a first end and a second end. The first end of the power processing circuit 102a is connected to an input voltage, and the voltage is output from the second end after being processed by the power processing circuit 102a. Thus, the voltage characteristics (e.g. voltage magnitude, duty cycle, and so on) of the voltage on the first end and the second end are different. The voltage output by the second end is controlled to be “on” or “off” by the switch 104a. Then, the output voltage is stabilized by the first capacitor 106a and then adjusted by the linear voltage regulator 108, and is stabilized by the second capacitor 116a again. Finally, the required output voltage is obtained.
The power circuit of FIG. 1b performs the voltage regulation first, and then performs the voltage transformation process. As shown in FIG. 1b, the power circuit 100b includes a linear voltage regulator 108b, a first capacitor 106b, a switch 104b, a power processing circuit 102b, and a second capacitor 116b. The linear voltage regulator 108b adjusts the power voltage first, and then maintains the output voltage at a certain predetermined value, and the output voltage is stabilized by the first capacitor 106b. Then, the switch 104b controls whether to turn on or off the output voltage to the power processing circuit 102b. The power processing circuit 102b has a first end and a second end, in which the voltage of the first end is processed by the power processing circuit 102b and then output from the second end. Thus, the voltage characteristics of the voltage on the first end and the second end of the power processing circuit 102b are different. The power processing circuit 102b can further have a third end, for example, coupled to an input voltage. The power processing circuit 102b changes the voltage on the first end of the power processing circuit 102b according to the input voltage, so as to obtain the voltage on the second end of the power processing circuit 102b. The voltage output from the second end is stabilized by the second capacitor 116b again, and finally the required output voltage is obtained.
FIGS. 2a and 2b show double charge pumping circuit corresponding to FIGS. 1a and 1b of the conventional art respectively.
The double charge pumping circuit in FIG. 2a firstly performs a double voltage transformation, and then performs the voltage regulation process. As shown in FIG. 2a, the components are approximately the same as those of FIG. 1a, so the same components will not be described herein again. The power processing circuit 102a includes a first switch 202a, a second switch 204a, a capacitor 206a, and a third switch 208a. The first switch 202a and the third switch 208a in the power processing circuit 102a are “on” in a phase 1, and the second switch 204a and the switch 104a are “on” in a phase 2. The “on time” controlled by the phase 1 and the phase 2 is different. Thus, the voltage transformation process is performed on the input voltage Vx (Vx>Vin) connected to the first switch 202a. In the phase 1, the Vx voltage is obtained at the output of the power processing circuit 102a, and in the phase 2, a 2Vx voltage is obtained. Therefore, a relative stable 2Vx voltage can be obtained through the switch 104a and the first capacitor 106a, and then the linear voltage regulator 108a and the second capacitor 116a perform the voltage adjustment and stabilization. Finally, the 2Vin output voltage is obtained.
The double charge pumping circuit in FIG. 2b firstly performs the voltage regulation and then performs the double voltage transformation process. As shown in FIG. 2b, the components are approximately same as those of FIG. 1b, so the same components will not be described herein again. The power processing circuit 102b includes a second switch 204b, a second capacitor 206b, a third switch 208b, and a fourth switch 210b. A stable Vin voltage is obtained through the linear voltage regulator 108b and the first capacitor 106b. The switch 104b and the third switch 208b in the power processing circuit 102b are used together and are “on” in the phase 1, and the second switch 204b and the fourth switch 210b are “on” in the phase 2. The “on time” controlled by the phase 1 and the phase 2 is different. Therefore, a 2Vin voltage is obtained at the output of the power processing circuit 102b, and is stabilized by the second capacitor 116b. Finally, the stable 2Vin output voltage is obtained.
FIG. 3 shows a negative-voltage charge pumping circuit according to the conventional art. The circuit performs the voltage transformation process first and then performs the voltage regulation. As shown in FIG. 3, the negative-voltage charge pumping circuit 300 includes a first switch 302, a second switch 304, a first capacitor 306, a third switch 308, a fourth switch 310, a second capacitor 312, a linear voltage regulator 314, and a third capacitor 322. The first switch 302, the second switch 304, the first capacitor 306, and the third switch 308 forms a negative-voltage generating circuit (corresponding to the power processing circuit in FIG. 2a). The action principle of the circuit in FIG. 3 is approximately the same as that of FIG. 2a, so the details will not be described herein again. When the circuit enters the phase 1, the first switch 302 and the second switch 304 are “on”, the input voltage charges the first capacitor 306 until the voltage becomes Vx, and the third switch 308 and the fourth switch 310 are “off”. When the circuit enters the phase 2, the third switch 308 and the fourth switch 310 are “on”, the first switch 302 and the second switch 304 are “off”, and the voltage is changed to be −Vx. Therefore, the output voltage can be maintained at a predetermined value −Vin by the linear voltage regulator 314 and the third capacitor 322.
The power circuit of the present invention modifies the above disadvantages.